For a wide variety of applications, chairs are nowadays provided with features which provide enhanced comfort to the person using the chair. For illustration, office-type chairs are commonly utilized in modern working environments to provide an occupant with a level of comfort while performing certain tasks that require a person to be in a seated position for an extended period of time. One common configuration for such a chair includes a mobile chair base assembly to allow the chair to roll across a floor and a pedestal column supporting the superstructure of the chair. The superstructure may include components which enable the user to adjust certain settings of the chair and to facilitate recline or “tilt” of the chair superstructure, including the back and frequently also the seat of the chair. Such a chair configuration allows users to change their sitting position in the chair as desired. Fatigue may be reduced during long sitting periods.
In recent years, chair designs have implemented a feature where a chair back exerts an increasing force onto the seat occupant as a function of recline angle, during a rearward reclining movement of the chair back. The chair seat may also tilt in this process or may be displaced otherwise relative to the chair base. To this end, a spring may be provided which is compressed when the chair back reclines. The torque which must be exerted onto the chair back to maintain the chair back at a given recline angle increases as a function of recline angle. Vice versa, the force exerted onto the occupant by the chair back increases.
For enhanced comfort, it is desired that the force applied by the chair back can be adjusted. For illustration, a light-weight user may prefer a configuration which requires less force to be applied onto the chair back to recline it by a given angle. A heavier user may prefer recline characteristics which requires him to exert a greater force onto the chair back to recline it by the same given angle. The chair may have a tension adjust system which allows the torque which must be exerted onto the chair back in a recline movement, as a function of recline angle, to be adjusted.
One approach to implement such a tension adjust system is to alter an offset bias or pretension of the spring. This can be attained by altering an offset-compression of the spring. An offset force can thus be added to the force applied by the spring. Such an approach has various shortcomings. For illustration, it may be a considerable challenge to adjust the offset bias in a state in which the chair back is already reclined and the spring is already compressed to a certain degree. For further illustration, adjust mechanisms that allow the offset bias to be adjusted frequently need to be implemented such that an actuating lever must complete several full turns, often more than five turns, to alter the recline characteristics from the softest to the hardest recline characteristics. For further illustration, depending on the arrangement of the spring on the chair, an adjust mechanism which adjusts an offset bias may make it difficult for the user to adjust the recline characteristics while remaining seated on the chair.
Another shortcoming of an adjust mechanism which alters an offset bias is that the torque curve as a function of recline angle is merely shifted by an offset. It may be desirable to provide an adjust mechanism which provides enhanced versatility in adjusting the recline characteristics from soft to hard.
There is a need in the art for a tilt mechanism and for a chair which provide good support to the user during a reclining motion. There is a need in the art for such a tilt mechanism and chair which allow the recline characteristics, i.e., the torque as a function of recline angle of the chair back, to be adjusted in a versatile manner. There is also a need for such a tilt mechanism and chair in which the adjust mechanism for adjusting the tension applied by the chair back can be actuated more conveniently, also in a state in which the chair back is already reclined.